The oxygen-increasing machine is the life-saving and facilitation equipment for fish and shrimp. Existing mechanical oxygen-increasing machines mainly include three types, that is, the waterwheel type, impeller type and water-spraying type. The waterwheel type is used in more fields. The existing waterwheel oxygen-increasing machine adopts the arrangement that an integral bracket is connected to the floating bodies, and the power devices such as the engine, reduction gearbox, etc., are installed on the integral bracket, which leads to inconvenient assembly and disassembly. For instance, the U.S. Pat. No. 6,634,626B2 and U.S. Pat. No. 5,116,501A are inventions that adopt the solution of integral bracket being connected to floating bodies, which must use stainless steel to manufacture the machine for the purpose of preventing corrosion by seawater. Therefore, the machine is heavy in weight, which affects the buoyancy of the floating bodies and is expensive in price. Moreover, the power and volume of existing waterwheel oxygen-increasing machines are not adjustable. Impellers are an integral structure with a fixed number of blades and nonadjustable lengths of axial direction of impellers. It has many disadvantages such as a complicated manufacturing process, high cost, narrow applicable scope and bad general usage properties.